The present invention is generally related to sensing devices, and, more particularly, to tire pressure monitoring system and techniques for transmitting information to such a system in the interior of a tire from an external device.
A pressure sensor is one important component of a direct tire pressure monitoring system (TPMS), such as may be prescribed by governmental regulations. See, for example, 49 CFR Part 571, Titled “Federal Motor Vehicle Safety Standards: Tire Pressure Monitoring Systems; Controls and Displays”. One basic configuration of a direct TPMS generally includes various components, such as a transmitter (not necessarily a transceiver, in order to reduce system costs) and a microprocessor that may be assembled within the interior of the tire. Most direct TPMSs are self-powered by a battery.
To reduce power consumption, the TPMS is commonly configured to operate within relatively long silent time intervals between transmissions. This type of operation with long silent time intervals between transmissions may create the following issues. Firstly, sensor test time may be unacceptably long due to the long silent interval between transmissions. Secondly, communications from an external source into the TPMS may be problematic since the transmitter is not generally designed to receive signals, but is designed just to transmit them. Communications from an external source or device may be useful for supplying various types of information to the TPMS, such as training the system to know sensor location in the vehicle, e.g., Front right, Front left, Rear right, Rear left, spare tire location, or performing calibration of the pressure sensing device, if optionally desired, etc. In view of the foregoing issues, it would be desirable to provide reliable and low-cost circuit and techniques that allow communicating information, for example, to the micro-processor of the TPMS for performing various operational functions, such as testing, calibration (if optionally desired), TPMS training, etc., without having to use an incrementally costlier device, such as a transceiver.